The present invention relates to ink printers that deposit ink images onto a print medium, and in particular relates to managing the quantity of ink remaining in an ink container for such a printer.
Many types of ink printers eject ink onto a print medium, such as paper, in controlled patterns of closely spaced dots. To form color images, multiple groupings of ink jets are used, with each group being supplied with ink of a different color from an associated ink container. Ink printers use different techniques to eject ink from a printhead onto the print medium. Ink printing techniques use mechanism such as thermal, acoustic, piezo-electric, or other types of energy to eject ink droplets that form the dots on the print medium, creating the printed image.
Thermal ink jet printers use thermal energy to vaporize momentarily ink in an ink channel nozzle and form bubbles on demand. Resistors located in capillary filled ink channels near a channel terminating nozzle or orifice generate the thermal energy to vaporize the ink into bubbles in the channel. Each temporary bubble expels an ink droplet from the nozzles, and propels the ink droplet from the printhead toward the recording medium. The printing system may be incorporated in either a carriage type printer or a page width type printer. A carriage type printer generally has a relatively small printhead containing the ink channels and nozzles. The printhead is attached to an ink supply container, which is typically carried on the same carriage as the printhead. The carriage with the printhead and container is reciprocated across a print region to print one swath of information at a time on a recording medium that is held stationary on a platen. After the swath is printed, the medium is stepped a distance equal to the height to the printed swath, so that the next printed swath will be contiguous with the previous printed swath. The procedure is repeated until the entire page is printed. In contrast, the page width printer has a stationary printhead having a length equal to or greater than the width of the recording or print medium. The print medium is continually moved at a constant speed past the page width printhead in a direction normal to the printhead length.
Attempting to eject ink drops when no ink is available at the printhead may damage the printhead. Therefore, printing should stop before the ink container is empty. When an ink printer and the user of such an ink printer are aware of the quantity of ink remaining in a particular ink container, the printer can reduce the possibility of attempting to print after the ink container is empty.
U.S. Pat. No. 5,997,121 describes a system and method that detects a low level of ink in an ink container, and provides a low ink level warning signal. The system and method described there determine when the level of ink in an ink container has fallen below a particular threshold. Once the printer detects a low ink level in the ink container, the printer can manage ink usage, and reduce the possibility of continuing to attempt to print using that ink container after the supply in the container has been exhausted. The ink level detecting takes place in a maintenance station, which typically is outside the normal printing range of the carriage. Thus, detecting the ink level in the container requires that the carriage carrying the printhead and ink container be moved out of the printing range. This movement takes time, and thus may slow certain print jobs. Therefore, printers balance frequent measurements of the ink level, to maintain an accurate measure of the quantity of ink remaining in the ink container, with delays introduced into the printing process caused by the measurement process.
Many printers perform an ink level detection at the end of each print job, when the cartridge carriage is typically moved into the maintenance station for other maintenance purposes, such as cleaning the printhead. During lengthy printing jobs, such as multi-page printing jobs, some printers direct the printhead carriage into the maintenance station to perform ink level sensing at intervals based on the number of pages printed. For example, the printer may perform an ink level measurement after a predetermined number of pages, such as after each page. However, determining the appropriate number of pages between successive measurements of the ink level tends to produce inexact results, as different print jobs may apply significantly different amounts of ink to each page, and even within a single print job, different pages may have significantly different quantities of ink applied to them.
An ink printer includes a printhead for depositing ink onto a print medium, an ink container connected to the printhead for supplying ink to the printhead, and an ink level sensor for measuring the level of ink in the ink container. An ink level sensor activator measures the approximate quantity of ink deposited by the printhead, and periodically causes the ink level sensor to measure the level of ink in the ink container after the printhead has deposited a predetermined quantity of ink.
In an ink printer having a printhead, an ink container connected to the printhead for supplying ink to the printhead, and an ink level sensor for measuring the quantity of ink in the ink container, a method of determining when the ink level sensor should measure the quantity of ink in the ink container includes measuring the quantity of ink ejected by the printhead, periodically determining if the quantity of ink ejected by the printhead has succeeded a predetermined threshold, and, if the quantity of ink ejected by the printhead has exceeded the predetermined threshold, measuring the quantity of ink in the ink container.